Photos: Protests against the Keystone XL pipeline in the U.S.

Photos from protests against the Keystone XL pipeline on February 17, 2013. The TransCanada Corp pipeline would link the oil sands of northern Alberta, the world's third largest crude resource, to refineries and ports in Texas. Environmentalists say approval of the pipeline will encourage more development in the oil sands, where extraction is carbon intensive, leading to greater greenhouse gas emissions.